Electrical resistance with at least two contact fields on a ceramic substrate and process for manufacturing the same

ABSTRACT

A temperature-dependent measuring resistance with rapid response time is at least partially arranged on an electrically insulating surface of a ceramic substrate, wherein a portion of the conductor path spans a recess situated in the substrate in a bridge-like manner, and the remaining portion of the conductor path in the edge area of the substrate adjacent to the recess is provided with connection contact fields. The conductor path comprises a platinum or gold layer, wherein the conductor path is partially provided with a cover layer of glass, and wherein the connection contact fields are exposed. In a further embodiment, the conductor path is arranged together with the connection contact fields either on a screen-printed glass membrane or on a thin film membrane applied in a PVD process, which covers the surface of the ceramic substrate and spans the recess. The cover layer is likewise selectively applied by screen printing in case there is a glass membrane. In the case of a thin film membrane, the cover layer is also applied selectively by a PVD process and can be the same material as the thin film membrane. The ceramic substrate preferably comprises aluminum oxide.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of International ApplicationPCT/EP97/06757, filed Dec. 3, 1997, the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention concerns an electrical resistor, especially atemperature-dependent measuring resistance with rapid response time,having a conductor path (printed circuit) provided with at least twoconnection contact fields, which are arranged on an electricallyinsulating surface of a substrate, wherein a portion of the conductorpath spans at least one recess of the substrate in a bridge-like manner,and the conductor path is arranged in a plane. The invention alsorelates to a process for manufacturing the electrical resistor.

A temperature measuring arrangement (radiation thermometer) is knownfrom German published patent application DE 39 27 735 A1 with atemperature-sensitive thin film resistance, which is appliedmeander-shaped to a plastic sheet which is stretched over a cavity of asubstrate material. A circuit board or a carrier of epoxide resin isprovided as a substrate. Such a temperature measuring arrangement isonly suited for use in an environment with temperatures below 200° C.,owing to the low thermal stability of synthetic resin.

Furthermore, from German published patent application DE-OS 23 02 615, atemperature-dependent electrical resistor of resistance material isknown, which forms a winding conductor path as a thin layer, which isapplied over a thin foil. The foil made of polymer plastic spans withits uncoated side a recess in a carrier element which, for example,consists of copper, wherein the recess has the same shape as theconductor path and aligns with it in a direction perpendicular to thefoil plane. Here, it is a matter of a temperature measuring arrangementwhich requires a high technical expenditure for the requisite preciseoverlaying of conductor path and recess.

It is known from German patent DE 30 15 356 C2 that electric circuits inthick layer technology are preferably manufactured on ceramic,plate-shaped substrates by imprinting pastes whose active materialconsists of metal powders, glass or glass ceramic powders, or mixturesof glass and metal oxides. For manufacturing rapidly responding sensorsfor temperature measurement, temperature-sensitive thick layer resistorsare applied to self-supporting layers, which are obtained by pastescreen-printing with the aid of a filler gasifiable under the action oftemperature and cover a subsequently formed hollow space. Here, it is aquestion of a relatively expensive process.

Furthermore, from German published patent application DE 38 29 765 A1 orU.S. Pat. No. 4,906,965, a platinum temperature sensor is known, inwhich a platinum resistance path with at least two ends is mounted on asurface of at least one ceramic substrate. For manufacturing it, aplatinum conductor path in the form of a meander-zigzag pattern isapplied to the inner surface of a ceramic sheet and subsequently shapedinto a roll, wherein breaks with adjusting bridges are provided betweenadjacent points of the conductor path pattern for the purpose ofadjustment. The ceramic substrate is fired together with the appliedplatinum resistance. The platinum resistance is resistant toward theambient atmosphere and moisture owing to sealing measures. In addition,after adjustment, the lead-in openings and conductors necessary for thisare sealed off by means of a ceramic coating or glass paste. Thecomparatively high heat capacity turns out to be problematic with suchan arrangement, which does not make possible a rapid response withsudden temperature changes, without further measures, and whichreproduces an exact measured value only after execution of a transitionfunction.

A further embodiment of a resistance element as rapid temperature sensoris known from German published patent application DE 38 29 195 A1. Here,the resistance element is constructed as a layer resistor of platinumpaste, which is accommodated in a bubble made of glass ceramic, which isarched on an electrically insulating ceramic substrate. Here, theself-supporting arched resistor layer is to be regarded as problematicwith respect to mechanical stresses, for example, shock, pressure orvibration during use in harsh environments.

SUMMARY OF THE INVENTION

An object of the invention is to provide resistors insensitive towardouter mechanical stresses for rapid-responding temperature sensors,which are especially suited as sensors for rapidly changing temperaturesin gas masses in the temperature range of -100 to +800° C. Furthermore,with temperature sensors of this type, rapid gas mass measurers withmicrostructures are constructed, whose reaction time lies in themillisecond range.

This objective is accomplished in accordance with an arrangement whosesubstrate is formed from ceramics or glass and whose conductor path isfastened in the edge area of the substrate adjacent to the recess on theelectrically insulating surface of the substrate. The high longevity ofthe sensor proves to be especially advantageous.

In a preferred embodiment, the conductor path is constructed in theshape of a meander (at least in the area of the recess), wherein therespective return areas of the meander are fastened in the edge area ofthe recess on the electrically insulating surface of the substrate,while the intermediate stretches of the meander span the recess in abridge-like manner. The conductor path, in a preferred embodiment, ismade of a platinum layer/Pt foil, which has a thickness in a range of 1to 6 μm, preferably 2.5 μm.

It proves to be especially advantageous herein that, owing to themass-poor structure, the sensor signal follows the rapidly changingmeasurement parameters almost inertia-free.

In a further preferred configuration of the resistor arrangement of theinvention, the conductor path comprises a gold layer, wherein the goldlayer has a thickness in the 1 μm to 8 μm range, preferably 2 μm to 3μm. The manufacture of a structured gold layer proves to beadvantageous, since galvanic deposition processes are state of the art,even for fine structures according to various processes.

In a further advantageous embodiment of the resistance arrangement, theelectrical conductor path is installed on a plate-shaped membrane atleast partially covering over the recess, wherein the membrane has athickness in the 1 μm to 50 μm range. Here, the increased stability ofthe conductor path proves to be advantageous, as can be requiredespecially in cases of severe mechanical stress, for example vibration.

The membrane comprises either a glass layer, which has a thickness of 10μm to 50 μm, or it preferably is made of an SiO or TiO₂ layer, appliedin a thin layer process, wherein it has a thickness of 1 μm to 10 μm,preferably a thickness of 2 μm. Owing to the comparatively thinmembrane, advantageously a low thermal inertia and consequently a rapidresponsiveness are guaranteed.

In a further advantageous embodiment, the conductor path on thesubstrate is provided with a cover layer of an electrically insulatingmaterial, which has a thickness in the 1 μm to 50 μm range. Theconductor path is thereby protected, particularly in an aggressiveenvironment, so that long-term stability increases. The cover layer ofthe conductor path comprises either glass with a thickness of the glasscover layer in a range of 10 μm to 50 μm, or a layer applied by means ofa thin film process, wherein the cover layer advantageously comprises anSiO layer, which has a thickness of 1 μm to 10 μm, preferably athickness of 2 μm. Owing to the comparatively thin cover layer, a rapidresponsiveness as a temperature measuring resistance exists, wherein itsouter surface is protected against interventions from the ambientatmosphere.

The above objective is accomplished according to a first process, inwhich a recess is created in a ceramic substrate, and this is filled byfiller material of glass paste, glass ceramic, glass solder, silver,indium, nickel or a silver-nickel alloy, and the filling thus introducedis made level with the outer surface of the substrate. Subsequently, aconductor path of platinum or gold is applied to at least one portion ofthe electrically insulating constructed substrate surface; and thefiller material is thereafter etched away, so that the metal conductorpath spans the recess in a bridge-like manner in a plane. It proves tobe especially advantageous herein to use indium as a filler material,since it can be very easily leveled off and can be chemically removed bymeans of a mixture of 45 g/l Ce(SO₄)₂, 160 g/l HNO₃, 80 g/l H₂ SO₄,preferably at a temperature of 60° C.

The objective is accomplished in accordance with the invention accordingto a second process, wherein a recess is created in a ceramic substrate,and this is filled with filler materials of glass pastes, glassceramics, glass solder, silver, indium, nickel or a silver-nickel alloy,and the filling thus introduced is made level with the outer surface ofthe substrate. A flat membrane is subsequently applied to the surface ofthe substrate by a screen printing or thin film process, and followingthis, a conductor path of platinum or gold is applied on the glassmembrane galvanically or in a thin film process. Thereafter, astructured cover layer is at least partially applied to the conductorpath, and finally, the filler material situated in the recess is etchedaway. Here also, the use of indium as a filler material is best suited.

In a preferred embodiment of the process, the membrane is applied to thesurface of the substrate in a screen printing process as a glassmembrane or in a thin film process as a thin film membrane of SiO.Consequently, the usual coating techniques can be used advantageously.In addition, the structured cover layer is applied to the conductor pathin a screen printing process as glass or in a thin film process as athin film layer of SiO.

In a preferred embodiment of the process, the recess is created bysawing at a depth range of 20% to 60% of the thickness of the substrate.It is, however, also possible to cut out the recess by a laser beam, sothat it includes the entire substrate thickness. Such a process isadvantageously used for a mass production of resistors with lowmanufacturing tolerance, since the later following chemical etchingintervention for removing the filler material can take place verycarefully (from the backside).

Preferably, glass pastes with approximately the same expansioncoefficients as the substrate are applied as a cover layer on theconductor path and substrate and fired at a temperature in the 500° C.to 1000° C. range, especially 850° C. to 920° C. in a continuous heatingfurnace for a period of time of about 20 minutes. The comparativelysimple mass production hereby proves to be advantageous.

Furthermore, the conductor path is preferably applied in a thin filmprocess and structured by means of photolithography, ion etching andremoval of photoresist. It moreover proves to be advantageous hereinthat a high precision of the resistance can be attained.

It is, however, also possible to deposit the conductor path galvanicallyin a resist channel on a previously applied metal electrode, and finallyto remove the metal electrode chemically or by a dry etching process. Itmoreover proves to be advantageous that this process can run at lowtemperatures, so that the formation of cracks between the levelled-offfiller material and the substrate is prevented. Alternatively, theconductor paths can be filled by a PVD process with Pt and subsequentlyseparated by a lift-off technique.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe invention, will be better understood when read in conjunction withthe appended drawings. For the purpose of illustrating the invention,there are shown in the drawings embodiment(s) which are presentlypreferred. It should be understood, however, that the invention is notlimited to the precise arrangements and instrumentalities shown. In thedrawings:

FIG. 1 shows in a perspective representation a first preferredembodiment of an electrical measuring resistor of the invention;

FIG. 2 shows a cross section through the longitudinal axis along lineII--II in accordance with FIG. 1;

FIG. 3 shows a resistor manufactured according to an alternativeprocess, in which the recess is created in the ceramic substrate bylaser cutting;

FIG. 4 shows in perspective representation a further preferredembodiment of the invention, in which the platinum structure of themeasuring resistance is applied on a membrane, which is situated on thesurface of the substrate;

FIG. 5 shows a cross section through the longitudinal axis along theline V--V according to FIG. 4;

FIG. 6 shows the course over time of the rise in voltage (voltage U as afunction of time t), wherein the sensor is acted upon by a current of0.07 A. The time scale amounts to 0.5 ms/div or partition for curves (a)and (b), 5 ms/div for curve (c), and 5 s/div for curve (d);

FIG. 7 shows a resistor in which the conductor path is applied as ameander of platinum or gold on a thin film membrane, and is passivatedby a cover layer in the area of the recess;

FIG. 8 shows a response time determination (voltage U as a function oftime t) for a resistor with a conductor path as platinum meander ofthickness 1.7 μm in accordance with FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with FIGS. 1 and 2, the ceramic substrate 1 comprises aboard-shaped block with an electrically insulating surface on the basisof ceramics or glass. The substrate 1 is provided with a recess 3 alongits central axis 2, which is spanned in a bridge-like manner by aconductor path 4 serving as a measuring resistance, wherein portions ofthe conductor path 4 are fastened on the substrate in the edge area ofthe substrate toward the recess. The conductor path is provided on itsrespective ends 5 and 6 with connection contact fields 7, which servefor connection with an electrical evaluation circuit. Since theconductor path with its thickness of about 2.5 μm has an extremely smallheat capacity, it can pick up extraordinarily rapidly the temperature ofthe surrounding atmosphere in the area bridging the recess 3, or of thegas atmosphere flowing through the recess 3, and consequently provideadvantageously for a rapid evaluation or indication of thermal changes.

Furthermore, it is advantageously possible to record the gasesselectively by application of a catalytic material on a conductor pathconstructed as a platinum foil.

Substrate 1 here comprises an aluminum oxide ceramic with 99.6 wt % Al₂O₃ and has a thickness in the 0.1 to 1.0 mm range. Preferably, thethickness of the substrate lies in the 0.6 to 0.7 mm range. The width ofthe recess 3 preferably lies in the 0.5 to 1 mm range, the depth of thesame in the 0.1 to 0.4 mm range. The conductor path 4 comprises aplatinum layer with a thickness of about 2.5 μm, wherein a glass coverlayer 8 is applied by a screen printing process to the platinum layer inthe support area of the substrate 1, wherein the ends 5, 6 of theconductor path 4 are left free from the glass cover layer and areprovided with a gold layer, likewise applied by a screen printingprocess, as connection contact fields 7.

For manufacture, in a ceramic substrate 1 of aluminum oxide, having athickness of 0.6 to 0.7 mm, preferably 0.635 mm linear milled slots arecreated for recess 3 with a breadth of 0.78 mm to a depth of 0.3 mm. Themilled slots are first partially filled, by metered injection with glasspastes of various types, to a milling depth of three fourths and driedfor an hour at a temperature of 180° C. Subsequently, they are fired ata peak temperature of about 850° C. for 20 minutes in a continuousheating furnace with compressed air flowing through. Thereafter, asecond filling of the milled slots takes place such that, after reneweddrying and after renewed firing of the glass paste at the sameparameters as with the first filling, an overfilling of about 0.1 to 0.2mm of the milled slots in substrate 1 exists. This means that thefilling projects about 0.1 to 0.2 mm above the outer surface of thesubstrate.

Thereafter, the still projecting fired glass paste is ground down in awet process using silicon carbide grain sizes of 350, 500, 800, 1200,2400 and 4000, so that the transitions in the ceramic substrate-glasspaste area possess so little unevenness, that it lies in the range ofless than 1 μm. Upon a microscopic observation, no crack between ceramicand glass is any longer recognizable, which could exert a negativeeffect on subsequent processes. The form-locking filling of the linearlyintroduced milled slots of recess 3 is, in the final analysis, to beattributed to the expansion coefficient of the glasses, which in thetemperature range considered amount to about 7.5×10⁻⁶ per degreeCelsius, and consequently almost correspond to the expansion coefficientof the aluminum oxide ceramic which is used for substrate 1.

After a cleaning process, these thus-filled substrates are vapordeposited with a metered platinum coating to a thickness of 1.5 μm to2.5 μm. Thereafter, according to the state of the art (for example, DE36 03 785 C2 or DE 42 02 733 C2), occur well known operations such asphotolithography, ion etching of the platinum, and removal of thephotoresist by means of incineration.

It has emerged upon microscopic examination that the platinum conductorpaths, with a width in the 10 μm to 15 μm range, in the transition areafrom ceramic to glass remain undamaged. Following structuring, theapplication of a suitable glass cover layer 8 (for example, IP 211 of W.C. Heraeus GmbH & Co. KG) as well as of the connection contact fields 7with a gold surface takes place by screen printing. The measuringresistances arranged on the multi-unit ceramic substrate are thenseparated into individual parts by a frame saw. Finally, the areasfilled with glass pastes are dissolved from the recesses 3 from the facesides in. This takes place by means of concentrated HNO₃ (65 percent) ata temperature of 50° C. A temperature sensor manufactured according tothis process has, for example, the following data:

RO=6.64 Ohm;

R100=9.12 Ohm;

Tk=3733 ppm/K, wherein the platinum is still untempered;

R.sub.□ =0.043 Ohm (square resistance);

[R.sub.□ is the quotient of the specific resistance ρ and layerthickness d (R=ρ/d).]

Conductor path width=50 μm;

Overall conductor path length: L=8.6 mm.

For determining the response time of the sensor, a measurement structureis used, in which a current generator switches on a current signal of0.100 A within a time of 0.5 ms to the sensor, which is situated in anambient atmosphere at a temperature of T=25° C. The heating of thesensor is held as a time-dependent voltage drop with a storageoscilloscope, from which the course of the temperature increase of thesensor can be determined over time. From the voltage U.sub.∞, theself-adjusting equilibrium temperature can be calculated.

A temperature sensor manufactured according to this process manifests arapid voltage rise to 0.73 volts, and as a consequence of the heating, afurther voltage rise to U.sub.∞ =0.860 V is obtained, which correspondsto a resistance of R.sub.∞ =8.60 Ohm and a temperature of T.sub.∞ =78°C. The temperature jump of ΔT=53° C. was reached within 3.2 ms (t 50%).

As an alternative to the process just described, process steps relyingon CIB (CIB=Chip in Board) technology can be used, or used in modifiedform, to produce a free meander structure of the conductor path. CIBtechnology is described, for example, in Nohr, W.-D. and Hanke, G.,"Reverse Beam-Lead Interconnections for Ultra High-Speed MultichipApplications," 5th International Conference & Exhibition on MultichipModules, Denver, USA (Apr. 17-19, 1996); and Hanke, G. and Nohr, W.-D.,"A New Chip Interconnection Technique for Ultra High Speed andMillimeter Wave Applications," 1996 IEEE MTTS International MicrowaveSymposium, San Francisco, USA (June 1996).

Following laser cutting of substrate openings in accordance with FIG. 3,a Cr/Au thin film metalization is applied by a PVD process after achemical edge cleaning. The substrate openings are then filled from thereverse side with indium. Thereafter follows a uniform photoresistcoating (thickness, for example, 6 μm), and subsequently the exposureand development of the resist. The conductor paths thus exposed are nowbuilt up, for example by a galvanic fine gold electrolyte, to athickness of, for example, 5 μm. After removing the resist, the basemetalization is removed by an ion etching process or in a wet chemicalprocess by differential etching. Finally, the introduced indium fillingis once again dissolved out chemically.

These process steps were modified so as to obtain a component with aself-supporting platinum conductor path structure. The Cr/Au basemetalization was thereby replaced by a platinum thin layer of 0.05 μm to0.1 μm applied by means of a PVD process.

Following the photostructuring process, a 1.5 μm to 3 μm thick platinumconductor path structure was deposited galvanically in an acid platinumelectrolyte. The platinum structures were separated by an ion etching.Finally, an additional tempering process of the platinum layer wasconducted. The further application of the cover and contacting layers 7,8 took place as described previously.

FIG. 4 shows an embodiment of the resistor in which the same substrate 1with recess is used, as in the previously explained first embodimentaccording to FIGS. 1 and 2. In contrast thereto, the surface of thesubstrate 1 was covered by a flat plate-shaped membrane 10 of glass,which closes off the recess 3 toward the top. On this membrane 10, theconductor path 4 is then applied as a platinum coating, wherein similarto the manner explained for FIGS. 1 and 2, the ends 5 and 6 of theconductor path are connected respectively with connection contact fields7, which are likewise applied to the membrane 10. The structure of theconductor path 4 is applied by a screen printing process, just as theglass cover layer 8. The overall thickness of the membrane 10 lies in arange of 10 μm to 50 μm. FIG. 5 shows a sectional representationperpendicular to axis 2 along line V--V of FIG. 4.

For manufacture, a silver profile wire with dimensions of 0.79 mm×0.28mm is cut to substrate size and embedded almost level into the recess bymeans of a 900° C. melting point glass paste, for example Type IP 156 ofW. C. Heraeus GmbH & Co. KG. Subsequently, a cover plate is fastened onthe substrate using two clamps. After this, the glass paste is dried ata temperature T=120° C. for two hours and fired at a peak temperature ofabout 920° C. for a period of 20 minutes. Then, a second screen print ofanother glass plate takes place with subsequent drying and firing at apeak temperature of 850° C. for a period of twenty minutes . From this,there results the already previously mentioned overall glass thicknessof the membrane 10 of 10 μm to 50 μm. After cleaning the glass surface,the process already described on the basis of FIGS. 1 and 2 is conductedup to the final separation of the individual substrates.

The individual elements are etched in concentrated nitric acid at atemperature of 50° C., in order to remove the silver profile band. Atemperature sensor produced according to this embodiment has thefollowing data, wherein the platinum thickness amounts to 2 μm:

RO=8.70 Ohm;

R25=9.54 Ohm;

R100=11.97 Ohm;

Tk=3754 ppm/K;

R.sub.□ =0.054 Ohm (square resistance);

Conductor path breadth=20 μm;

Overall conductor path length L=3.5 mm.

In accordance with FIG. 6, the same structure for measuring is used asaccording to the first embodiment. The sensor here is acted upon by acurrent of 0.07 A. A rapid voltage rise to U=0.67 V is thereby observedon the sensor under consideration within 0.5 ms. As a consequence of theadjusted heating, the voltage U.sub.∞ =1.2 V increases, whichcorresponds to a resistance of R.sub.∞ =17.14 Ohm and a temperatureT.sub.∞ =279° C. The temperature jump of ΔT=254° C. is reached within 5ms (t 50%).

The measurement curves attained for this embodiment are represented inFIG. 6. At a pure ohmic resistance of 6.8 Ohm (measuring curve a; timescale: 0.5 ms/div), no further voltage rise and consequently notemperature rise is recognizable following a generator-conditioned buildup time of about 0.5 ms. This behavior is fundamentally different withthe platinum sensor in accordance with embodiment 2. The measuringresistance heats up in accordance with the shown temporal measurementcurves b) (time scale: 0.5 ms/div), c) (time scale: 5 ms/div) and d)(time scale: 5 s/div) and reaches an equilibrium temperature of about279° C.

In the embodiment in accordance with FIG. 7, the membrane 10 is appliedby a PVD process at a thickness of 2 μm. In addition, a thin Ptelectrode with a thickness of 0.05 μm was applied in the same PVDprocess. After the photostructuring process, the conductor paths wereexposed. These were subsequently generated galvanically in an acid Ptelectrolyte at a thickness of about 1.8 μm. After removal of thephotoresist, the substrate was slit into the individual sensors in adiamond saw, and thereafter the indium filling in the square substraterecesses was removed in a wet chemical process. Now, a differentialetching of the platinum of about 0.1 μm was conducted by an ion etchingprocess, in order to separate the conductor paths electrically. Afterthis, a tempering took place. Selectively, a second SiO layer of thesame thickness was then applied as cover layer 8 by means of a PVDprocess. Then, a gold screen printing of the connection contact surfaces7 took place.

In a dynamic test, such a resistor manifests a behavior as shown in FIG.8. The values for this sensor amount to:

RO=9.17 Ohm;

R100=12.70 Ohm;

Temperature coefficient Tk=(R100-R0)/100·RO=3849·10⁻⁶ K⁻¹).

With the indicated electric currents, the platinum meander was heatedproceeding from room temperature to the temperatures indicated in FIG.8.

The time to attain 50% of this temperature jump is likewise indicated inFIG. 8 and for such a resistance t(50%)=5 ms.

A twenty hour temperature change test was additionally conducted withthis resistor. Here, the resistor was heated up electrically with afrequency of f=30 Hz during the 20 hours mentioned 2,160,00 times fromroom temperature to a temperature T=370° C. The resistor passed thistest undamaged.

It will be appreciated by those skilled in the art that changes could bemade to the embodiment(s) described above without departing from thebroad inventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiment(s) disclosed, butit is intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

We claim:
 1. A process for manufacturing a resistor, particularly ameasuring resistance for a rapidly responding temperature sensor, havinga conductor path provided with at least two connection contact fieldswhich are arranged on an electrically insulating surface of a ceramicsubstrate, wherein a portion of the conductor path spans a recess in thesubstrate in a bridge-like manner and the conductor path is arranged ina plane and wherein the conductor path is fastened on the electricallyinsulating surface of the substrate in an edge area of the substrateadjacent to the recess, the process comprising creating a recess (3) inthe substrate (1), filling the recess with a filler selected from thegroup consisting of glass pastes, glass ceramics, glass solder, silver,indium, nickel, and silver-nickel alloys, levelling the filling thusintroduced with an outer surface of the substrate (1), applying theconductor path (4) to the substrate galvanically or in a thin filmprocess as a platinum layer/Pt foil with a thickness in a range of 1 to6 μm or of a gold layer with a thickness in a range of 1 to 8 μm,subsequently applying a structured cover layer (8) at least partially onthe conductor path (4), and thereafter etching away the filler situatedin the recess (3).
 2. The process according to claim 1, wherein beforeapplying the conductor path (4) to the substrate, an additional flatmembrane (10) of a thickness in a range of 1 to 50 μm is applied to thesurface of the substrate by a screen printing or thin film process. 3.The process according to claim 2, wherein the membrane (10) is appliedto the surface of the substrate by a screen printing process as a glassmembrane or in a thin film process as a thin film membrane of SiO . 4.The process according to claim 1, wherein the structured cover layer (8)is applied to the conductor path (4) by a screen printing process asglass or in a thin film process as a thin film layer of SiO .
 5. Theprocess according to claim 1, wherein the recess (3) is created at adepth range of 20% to 60% of the thickness of the substrate.
 6. Theprocess according to claim 1, wherein the recess (3) is cut out with alaser beam and includes the entire substrate thickness.
 7. The processaccording to claim 1, wherein a glass paste is applied to the conductorpath (4) and substrate (1) as a cover layer with approximately the sameexpansion coefficient as the substrate (1), and these are fired at atemperature in a range of 500° C. to 1000° C. in a continuous heatingfurnace during a period of about 20 minutes.
 8. The process according toclaim 1, wherein as filler material a profile wire is used selected fromthe group consisting of silver, nickel and alloys thereof.
 9. Theprocess according to claim 1, wherein the conductor path (4) is appliedin a thin layer process and structured by photolithography, ion etchingand removal of photoresist.
 10. The process according to claim 1,wherein the conductor path (4) is galvanically deposited in a resistchannel on a previously applied metal electrode, and the metal electrodeis subsequently removed chemically or by a dry etching process.
 11. Theprocess according to claim 1, wherein the conductor path (4) isdeposited by a PVD process in a photolithographically generated resistchannel, and the photoresist is subsequently removed.